JPH07204419A - Method and device for filtrating and backwashing solid particulate from liquid - Google Patents

Abstract

PURPOSE: To provide a method and device for filtering and backward washing which may be utilized for filtering the entire circumference of a filter drum and is capable of executing efficient washing of filter media in spite thereof by backward washing. CONSTITUTION: The method for filtering and backward washing solid particles from liquid are executed by the filter drum 5, the entire part of which is disposed below a liquid surface 6 and which is covered the filter media 8 on the external wall surface and which allows the flow of the liquid through the external wall surface from the outer side to the inner side. The device is provided with a backward washing device for removing cake from the filter media. An air cushion 15 is inserted and formed in the filter drum 5 in order to start each backward washing cycle, by which the liquid is displaced in the filter drum 5 and the liquid is injected through an air cushion 15 to the rear surface side of the outer peripheral wall 7 of the filter drum 5 from an injector 19 having an injection head 17. The peeled cake is carried away to the outer side along an arrow 22 by the fluid flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter drum, which is entirely provided below a liquid surface, an outer peripheral wall is covered with a filter medium, and a liquid flows from the outer wall to the inner side of the filter drum, and filter residue is removed from the filter medium. And a backwashing device for filtering solid particles from a liquid. Such a device is used in particular as part of a purification device, for example a hydrodynamically overloaded device in which activated sludge particles in the aftertreatment tank are not completely settled and are then floated out of the aftertreatment tank. Used in.

[0002]

BACKGROUND OF THE INVENTION A method and a device of the type mentioned at the outset are known from Swiss Pat. No. 5,535,588. At that time, a filter drum which is wholly provided below the liquid surface is used. The outer peripheral wall of this filter drum is covered with a filter medium so that the liquid flows from the outside to the inside. At this time, the entire circumference of the outer peripheral wall is used for filtration. A backwash device is provided for removing the filter cake from the filter media. This backwash device comprises a suction head in the form of a suction strip. Since this suction head is provided outside in the lower range of the filter drum, the filter cake can be sucked out intermittently. The disadvantage here is that the cleaning action for the filter medium is limited by the suction output of the pump of the suction device. Due to the limited suction output, the filter material formed as a cloth is clogged and effective cleaning must be performed at regular intervals by injecting liquid under high pressure onto the filter material. Furthermore, this contamination shortens the filtration cycle and increases the wash water requirements. During washing through the suction device, the filter material in the form of a cloth is sucked in, which, after running for a long time, causes the cloth to stretch and close the suction head of the suction device.

From US Pat. No. 5,139,670 a device for filtering and backwashing solid particles from a liquid is known. In the case of this device, a filter drum is used through which the contaminated liquid flows from the inside to the outside. In that case, there is a drawback that the entire circumference of the outer peripheral wall of the filter drum cannot be used as a filtering surface at the same time. A backwash device is provided which operates on the jet head of the jet device and is located above the liquid level outside the filter drum.
As a result, the cleaning liquid is sprayed onto the filter material of the filter drum, so that the filter cake formed on the inner periphery is blown off and is carried out of the filter drum through the drop hopper and the conduit. The cleaning action obtained at that time is good. This is because the ejected liquid jet flow acts completely and without weakening because it works in the air chamber.

From EP 74966 a device is known for filtering solid particles from a turbid liquid, in particular wastewater in a purification plant. In this case, a flat filter plate is used instead of a filter drum. This filter plate is covered with a filter medium. A backwash device is provided with an ejecting device having an ejecting head on one side of the filter medium and a suction device having a sucking head on the other side.
The jet head and the suction head are guided along the filter plate or the filter medium and are sealed to prevent unintended suction of water. In this case, the structure of the filter plate complicates the device due to the sealing element and increases the cost. The contact between the filter plate and the filter medium and the jet head and the suction head causes large friction and wear of the filter plate and the filter medium. This has a negative impact on lifespan. The cleaning action provided by the jet head is limited. This is because the ejected liquid jet acts through the liquid cushion and is strongly damped before reaching the filter medium. When the washing capacity is exceeded in such a device, the filter medium is more and more blocked and the liquid level rises. This is disadvantageous because it increases the pressure difference, and there is a pinching action between the blocked filter medium and the mechanism of the cleaning device that moves relative to the filter plate, i.e. the jet head and the suction head, which results in a backwash device. No longer works.

[0005]

The problem underlying the present invention is that the entire circumference of the filter drum can be utilized for filtration and nevertheless an effective cleaning of the filter medium is carried out by backwashing. To provide a method and a device of the kind mentioned at the outset.

[0006]

In the case of a method of the kind mentioned at the outset, this task is based on the fact that an air cushion is inserted into the filter drum in order to start each backwash cycle, whereby the liquid is filtered. From a jetting device having a jetting head, which is displaced in the drum and provided unsealed inside the filter drum, the liquid is jetted through the air cushion to the rear side of the outer peripheral wall of the filter drum, and then separated. It is solved by the slag being carried away by the liquid stream.

The invention starts from the idea that the entire filter drum can be operated below the surface of the liquid, whereby the entire circumference of the filter medium can be utilized. During each backwash cycle, which is started or performed intermittently, an air cushion is formed below the liquid level in the filter drum. The air cushion is sized so that at least the outlet of the jet head and the rear side of the outer peripheral wall of the filter drum in the upper area of the filter drum are surrounded by air. Thereby, the liquid discharged from the ejecting head passes through the air cushion and hits the rear side of the outer peripheral wall of the filter drum without being damped by the liquid, thereby providing its cleaning action. This cleaning action takes place as strongly as if a part of the filter drum were submerged in the liquid level and the injection device was located above the liquid level, thereby operating in air. On the outflow side of the filter drum or filter medium, the jet head of the jet device operates in air,
Operates in liquid on the inlet side of the filter drum. There, a liquid stream is generated or prepared, which carries away the separated sludge. At that time, the liquid is used as a carrier medium for the separated sludge. This operation, which takes place in the air on the outlet side and in the liquid on the inlet side, both takes place below the liquid level. The jet head is provided in the upper area of the filter drum. That is, it is provided at a place where air bubbles are collected. The liquid stream for discharging the dregs is preferably likewise provided in the upper region opposite the jet head. By using air on one side and liquid on the other side, direct contact between the filter drum or filter medium and the backwash device is avoided, so that wear is avoided. The filter drum and the filter medium can be formed very easily. Sealing elements as required in the state of the art are omitted. In the case of this new method, surprisingly, the washing or backwashing effect is so great that no overloading of the washing volume occurs. Very dense sludge can be removed very effectively by this new method. This is because when the liquid sprayed from the nozzle to the filter medium during cleaning passes through the air cushion and the filter medium, air bubbles are generated, and this air bubble contributes to levitating the filter residue to the other side. .

The removal of the separated filter cake by means of a liquid stream outside the filter drum or filter medium can be carried out by several means. For example, the separated filter cake can be carried away by the suction head of a suction device provided without sealing. The edges of the suction head on the side of the filter media or the filter residue should be slightly separated from the filter residue. Thereby, the leaking water for the required liquid flow can be consciously sucked. Similarly, the air bubbles generated during cleaning have a negative effect on the suction device and must be sucked together with the leaking water. The kinetic energy of the leaked water carries away the separated slag.

The separated filter cake can be transferred into the floating tank without using a suction device. For that purpose, such a suspension tank can be connected outside the outer circumference of the filter drum in the upper region. The floating tank communicates with the surrounding liquid through the opening. Therefore, both liquid surfaces are at the same height position. The separated filter cake is carried from the nozzle through the air cushion to the floating tank through the liquid sprayed on the filter material.
The air bubbles generated at the same time assist this action.

The air cushion can be replenished during the backwash cycle, and can be replenished by the amount that air bubbles escape upwardly from the air cushion through the holes in the filter media of the filter drum. This allows liquid to be jetted from the jet head through the air cushion throughout the backwash cycle, maintaining the effectiveness of the wash.

The filter drum can be stopped when not backwashing. During the backwash, the filter drum is rotationally driven stepwise or continuously. Filtration continues uninterrupted during this backwash. The control of the backwash cycle depends on the highest and lowest water levels above the filter drum.

A suitable device for carrying out the method is according to the invention, in order to form an air cushion, a supply pipe for air reaching the interior of the filter drum is provided, in the upper region of the interior of the filter drum, the jet head. Is provided stationary and is supported unsealed against the outer peripheral wall of the filter drum. The air cushion can be formed above the ejection device with the ejection head.

The outlet or nozzle of the jet head provided along the generatrix of the filter drum over the entire working width is separated from the inner peripheral surface of the filter drum. However, an air cushion is formed in this area during the backwash cycle and is filled with liquid when no backwash is performed.

On the outside of the filter drum, above the jet head, the suction head of the suction device can be placed stationary and not sealed, but below the liquid surface, away from the filter medium of the filter drum. The suction head of the suction device is connected to a suction source via which the liquid and the debris contained therein can be carried away via the suction head and the connecting conduit. The suction device does not stop even in the case of a relatively thick layer of sludge.

Further, a floating tank can be connected and arranged outside the filter drum and above the jet head. The suspension tank is equipped with a device for discharging fine bubbles. As a result, a flow is generated in the floating tank, and the separated cake floats by the flow.

The floating tank has an overflow and communicates with the liquid surrounding the filter drum. Therefore, the water surface of the liquid to be filtered and the water surface in the floating tank are always kept the same, and fluctuate between the maximum value and the minimum value. At that time, the maximum value is determined so that the floating tank overflows and the floating solids are discharged and removed from the upper surface of the floating tank in a regular cycle. The release of microbubbles can be done by the pressure drop of air dissolved in water or by a pair of electrodes.

The filter drum can be rotatably mounted on its drain for the filtered liquid with its central axis oriented horizontally. The filter drum is always used with its central axis oriented horizontally. Thereby, the upper region is used to form the air cushion.
The filter drum is preferably rotatably mounted on the discharge tube. Thereby, various areas of the filter drum can be guided upwards and backwashed during the washing cycle.

The discharge pipe reaches the filtrate chamber. In the filtrate chamber, an overflow portion is provided below the liquid surface and around the filter drum. As a result, a pressure difference necessary for filtration is generated, so that the liquid can continuously flow through the filter medium.

[0019]

The present invention will be described in detail with reference to the preferred embodiments. A water channel 1 is shown schematically in FIG. This water channel can also be formed as a container or the like. A space 2 for the liquid to be filtered is provided in the water channel 1. This liquid reaches the space 2 through the inlet 3. A filter drum 5 is provided in the space 2 with its central axis line 4 being horizontal. This filter drum is provided below the liquid surface 6. The highest liquid level during filtration is shown as a solid line and the lowest liquid level is shown as a broken line. The liquid level 6 can fluctuate between these limit lines. Even at the lowest liquid level, the entire filter drum 5 always operates under water, and there is a pressure difference necessary for the flow of liquid. The filter drum 5 is provided with a filter medium 8 on its outer peripheral wall 7. The laying cylinder-shaped filter drum 5 may consist of a perforated plate or may comprise, for example, a square mesh fabric. A filter medium 8 in the form of, for example, a needle-shaped felt product, a metal woven fabric, a synthetic resin woven fabric or a synthetic resin foamed filter is mounted on this porous plate or woven fabric. Both end surfaces of the filter drum 5 are closed. In this case, the discharge pipe 9 penetrates one end surface. This discharge pipe is at the same time as the filter drum 5
Bearings for can be formed. The discharge pipe has a through hole inside the filter drum 5.
As a result, the liquid flows through the filter drum 5 from the outside to the inside and is discharged from the discharge pipe 9. The end of the discharge pipe 9 reaches the inside of the filtrate chamber 10. In this filtrate chamber, a pipe-shaped overflow portion 11 is provided, and the upper edge of the overflow portion 11 is
It is located at a position lower than the liquid level 6 in the space 2. As a result, a pressure difference necessary for the liquid circulation of the filter drum 5 is generated.

FIG. 2 shows a schematic cross section perpendicular to the horizontal axis 4. Outer peripheral wall 7 of filter drum 5 and filter medium 8
It can be seen that is provided below the liquid surface 6. The filter drum 5 can be driven intermittently in the direction of the arrow 12 or in the opposite direction via a rotary drive (not shown). In this case, the filter drum is preferably stationary while no backwash is performed. On the other hand, during the backwash cycle, the filter drum 5 continuously or intermittently moves in the direction of arrow 12. Filter drum 5
An air supply pipe 14 opens in the inner space 13 of the. This supply pipe is preferably guided through a discharge pipe 9. The supply pipe 14 serves to generate an air cushion 15 in the upper area of the inner space 13 of the filter drum 5 and to push the liquid. In the inner space 13 of the filter drum 5, an ejection head 17 having a nozzle 16 is fixedly installed. The jet head is connected to a liquid conduit 18 under pressure. This conduit is preferably guided through the outlet pipe 9. Liquid is injected into the conduit 18 via a pump, not shown, and controlled via a suitable valve to be injected via the nozzle 16. In this case, the jet flow must move exclusively through the air cushion 15, and therefore with great frictional action the inner surface of the filter drum 5 or its outer peripheral wall and the filter medium 8
Reach Therefore, the filter cake deposited on the outside of the filter medium 8 is effectively peeled off. Nozzle 16 mounted on jet head 17
Are extended over the entire width or the entire length of the filter drum 5. The nozzle, together with the jet head 17 and the conduit 18, form the main element of the jet device 19. The nozzle 16 of the injection device 19 is provided sufficiently far from the inner peripheral surface of the filter drum 5. Therefore, there is no risk of wear due to contact or the like. In this way, the required wide-range effect can be achieved via the nozzles 16 arranged side by side.

A suction device 20 is provided next to the injection device 19. This suction device has a suction head 21 as a main element. This suction head is fixedly arranged outside the filter drum 7, that is, in the direction opposite to the injection device 19. The free edge of the suction head 21 is provided apart from the filter drum 5 or the filter medium 8. Thereby, on the one hand, the suction head 2
1 and / or wear of the filter medium 8 does not occur. However, due to this separation, it is important that the liquid flow in the direction of the arrow 22 (see FIG. 3) carry away the sludge separated by the jetting device 19. The suction head 21 is connected to the conduit 23,
This conduit is guided to a suction source, for example a pump, which sucks and discharges the liquid and the separated cake.

FIG. 3 shows an enlarged upper range which is always below the liquid surface 6. The supply pipe 14 for the air cushion 15 can be guided upwards. Backwash can be performed as follows. When the liquid continuously flows through the filter drum 5 from the outer side to the inner side, solid particles are gradually deposited on the outer surface of the filter medium 8, so that the passing area of the liquid is gradually narrowed. Therefore, when the liquid to be filtered continuously flows in, the liquid level 6 rises until it reaches the set maximum value.
Also at that time, the liquid flows from the outside to the inside through the filter drum, and the filtered liquid is discharged through the overflow portion 11. When the maximum liquid level 6 is reached, the cleaning cycle is started,
First, air is supplied from the supply pipe 14 to form the air cushion 15, and at least the nozzle 16 of the injection device 19 is immersed in the air cushion 15. The liquid under pressure is jetted to the inner circumference of the outer peripheral wall 7 and the filter medium 8 via the conduit 18. Since the liquid jet flows only through the air of the air cushion 15, its kinetic energy is never weakened. Therefore, the liquid jet stream effectively peels off the filter residue on the outer surface of the filter medium 8. Since the suction device 20 is operating, the liquid is sucked out from the space surrounding the filter drum 5 according to the arrow 22 through the suction head 21 and the pipe 23.
This liquid carries the separated slag. During this washing cycle, the filter drum 5 is driven continuously or intermittently in the direction of arrow 12. In this case, the filter drum 5 can be driven to rotate once. Moreover, the cleaning cycle can be continued until the preselected minimum liquid level is reached. After effective cleaning of the filter media, the backwash cycle is stopped.

FIG. 4 shows another embodiment of the device.
In the inner space 13 of the filter drum 5, the same structure as that of the embodiment of FIGS. However, the suction device has been replaced by the flotation tank 24. This floating tank is provided or connected outside the filter drum 5 above the jetting device. The floating tank 24 is defined by the guide plates 25 and 26, but communicates with the liquid in the space 2 and further communicates with the liquid in the upper region of the filter drum 5. Therefore, the filter cake peeled off by the spraying device 19 floats up in the floating tank 24 by the arrow 27 and is carried away from the outer periphery of the filter medium 8. The air bubbles of the air cushion 15 passing through the outer peripheral wall 7 assist this process. A device 28 for discharging the fine bubbles 29 can be provided in the floating tank 24. This fine bubble is floating tank 24
Create or improve liquid flow in. The filter cake that has come off during the wash or backwash cycle
The liquid is collected on the surface in the floating tank 24 and is lifted together with the rising liquid surface 6. The floating tank 24 includes an overflow portion 30.
The floated slag over the overflow according to arrow 31 is discharged little by little in accordance with the cleaning cycle. Evacuation is also carried out via pipe 32. The raised slag can be carried away via a vacuum cleaner.

The backwash cycle is restarted after the maximum water level of 6 has been reached. At that time, first of all, the scum displaced in the previous backwash cycle is discharged over the overflow 30. The injection device 19 is activated and the filter drum 5 is rotated stepwise or continuously. At this time, since the filter medium 8 becomes clean, the filter medium can pass the liquid well, which lowers the liquid level in the space 2 and the liquid level in the floating tank 24. This is performed until the minimum water level shown by the broken line in FIG. 4 is reached. The air cushion 15 that is formed to initiate the backwash cycle is a floating tank 24.
It can be used to enhance and enhance the floating action of the separated sludge within. In doing so, a large air cushion 15 is formed to start the cleaning cycle or this air cushion is continuously replenished during the cleaning cycle so that the nozzle 16 is always immersed in the air cushion 15 or Need to be surrounded by. The washing of the filter medium 8 lowers the water level 6. Then, when the liquid level becomes the lowest, the backwash cycle ends.

[0025]

The filtration and backwash method and apparatus of the present invention is such that an air cushion is inserted into and formed in the filter drum to initiate each backwash cycle, thereby displacing the liquid in the filter drum. Liquid is jetted through the air cushion to the back side of the outer peripheral wall of the filter drum from the jet device having the jet head, which is provided inside the drum without being sealed, and the sludge thus peeled off to the outside by the liquid flow. Carried away. Therefore, the entire filter drum can be operated below the liquid level, thereby utilizing the entire circumference of the filter medium. Further, during each backwash cycle, an air cushion is formed below the liquid surface in the filter drum, so the jet flow passes through the air cushion and hits the filter medium without being braked,
Effective cleaning of the filter media can be done by backwashing.

[Brief description of drawings]

1 diagrammatically shows an arrangement of devices suitable for carrying out the method.

FIG. 2 is a vertical cross-section of the device with the main elements.

FIG. 3 is an enlarged view of the upper range of the filter drum.

FIG. 4 shows another embodiment of the device with the main components.

[Explanation of symbols]

 1 Water Channel 2 Space 3 Inlet 4 Central Axis 5 Filter Drum 6 Liquid Level 7 Outer Wall 8 Filter Material 9 Discharge Pipe 10 Filtrate Chamber 11 Overflow Part 12 Arrow 13 Inner Space 14 Supply Pipe 15 Air Cushion 16 Nozzle 17 Jet Head 18 Conduit 19 Injection device 20 Suction device 21 Suction head 22 Arrow 23 Conduit 24 Floating tank 25 Guide plate 26 Guide plate 27 Arrow 28 Device 29 Fine bubbles 30 Overflow part 31 Arrow 32 Pipe

Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location 29/38 510 C 520 C (72) Inventor Christian Fromman, Federal Republic of Germany, 92364 Dining, Waldstraße, 2

Claims (10)

[Claims] 1. A filter drum (5), which is wholly provided below a liquid surface (6), whose outer peripheral wall is covered with a filter medium (8), and through which liquid flows from the outer side to the inner side, and a filter medium (8). In a method of filtering and backwashing solid particles from a liquid with a backwash device for removing dregs, an air cushion (15) is inserted into the filter drum (5) to initiate each backwash cycle. The liquid thus displaces the air cushion (15) from an ejector (19) having an ejecting head (17), which is displaced inside the filter drum (5) and is provided inside the filter drum without sealing. A method characterized in that the filter cake (5) is sprayed to the rear side of the outer peripheral wall (7) of the filter drum (5) and is separated therefrom by the liquid flow. 2. Method according to claim 1, characterized in that the separated cake is discharged by means of a suction head (21) of a suction device (20) provided without sealing. 3. A process according to claim 21, characterized in that the separated filter cake is transferred to a suspension tank (24). 4. Method according to claim 1, characterized in that the air cushion (15) is replenished during the backwash cycle. 5. A drivable filter drum (5) which is wholly provided below the liquid surface (6), whose outer peripheral wall (7) is covered with a filter medium (8), and through which liquid flows from the outer side to the inner side. ) And a backwashing device for removing filter residue from the filter medium (8), the device for carrying out the method according to any one of claims 1 to 4 forming an air cushion (15). For this purpose, an air supply pipe (14) reaching the inside of the filter drum (5) is provided, and an injection device (19) equipped with an injection head (17) is installed in the upper area inside the filter drum (5). Device, which is mounted on the outer peripheral wall (7) of the filter drum (5) without being sealed. 6. A suction head (21) of a suction device (20) is placed above the jet head (17) outside the filter drum (5), not sealed, and of the filter drum (5). Device according to claim 5, characterized in that it is provided below the liquid surface (6), away from the filter medium (8). 7. A floating tank (24) is connected to the outside of the filter drum (5) above the jet head (17), the floating tank comprising a device (28) for discharging fine bubbles (29). The device of claim 5, wherein 8. Device according to claim 7, characterized in that the suspension tank (24) is provided with an overflow (30) and is in communication with the liquid surrounding the filter drum (5). 9. The filter drum (5) is rotatably supported on a discharge pipe (9) for filtered liquid with its central axis (4) horizontal.
Any one device of 8. 10. A discharge pipe (9) reaches the inside of a filtrate chamber (10), and an overflow portion (11) is arranged below the liquid surface (6) around the filter drum (5) in this filtrate chamber. 10. The device of claim 9, wherein the device is